I would assume that this depends on your "instrumented browser", and what methods its API offers.

perl -e 'system(q[opera --remote "openURL(http://www.perlmonks.org/)"]
+)'
[download]

I need to get the control back to my perl program. I guess the above call is a blocking call??

From the documentation on system:

Does exactly the same thing as exec LIST , except that a fork is done first and the parent process waits for the child process to exit.

Another alternative would be to use backticks instead of system. I personally consider this as a "quick" and "dirty" method even though I do use it a lot. There are some potential problems with using this method. Off hand I don't remember what all of the issues are, but I believe that there are better ways to launch another program and return control back to the Perl script without waiting for the launched program to return control.

Yes, it is a blocking call:

% perl -E 'system(q[opera http://www.perlmonks.org/]); say "hello!" ' 
+                               
hello!
[download]

That only prints "hello!" once Opera exists. Non-blocking alternatives are:

% perl -E 'system(q[opera http://www.perlmonks.org/ &]); say "hello!" 
+'
hello!
[download]

i.e. launching in the background, or

% perl -E '$r = fork; if($r == 0) { exec(q[opera http://www.perlmonks.
+org/]) } elsif(defined $r) { say "hello!" }'
hello!
[download]

which forks off a child process, and uses exec (so the child process doesn't hang around waiting for the browser process to end).